Highly-efficient freezing apparatus and highly-efficient freezing method

ABSTRACT

An object accommodated in an internal space of a freezer is quickly cooled to a predetermined temperature with preventing water from freezing while an oscillating electric field of, preferably, a variable frequency in the range of 50 Hz to 5 MHz and/or a magnetic field are applied to the object, or further ionic air is added to clod air, and subsequently the object is instantaneously frozen at the predetermined temperature. Preferably, the magnetic field is a static magnetic field and/or a variable magnetic field.

TECHNICAL FIELD

The present invention relates to methods for freezing foodstuffs, foodproducts, organisms, and other materials, and particularly to a freezingapparatus for producing highly fresh, high-quality frozen products and afreezing method in the freezing apparatus that can maintain thefreshness of the material while preventing the destruction of the cellsof the material.

High-performance freezing herein refers to a process producing highlyfresh, high-quality frozen product while preventing the destruction ofthe cells of the material to maintain the freshness.

The present invention also relates to a freezing apparatus for frozenproducts and refrigerated or fridge-frozen preserves, such as those offoodstuffs, food products, and organisms, and particularly to a variablemagnetic field generator capable of uniformly applying a variablemagnetic field to objects to be frozen.

BACKGROUND ART

In order to preserve foodstuffs, food, organisms, and other materialswith freshness maintained for a long time, frozen storage has beenconventionally applied. However, known frozen storage cannot perfectlyprevent changes in color tone of frozen materials, deterioration intaste, and occurrence of dripping. More specifically, it cannot preventdeterioration of the quality or freshness due to, for example, drippingresulting from thawing. Materials to be frozen, such as foodstuffs, foodproducts, and organisms, contain a large amount of water. The watercontained in these materials is constituted of bound water tied toprotein or other molecules in the materials and free water freelytransferring in the materials without being tied to the molecules. Infreezing, the free water is frozen, so that ice crystals grow. If theice crystals grow coarse, the cells of the materials are destructed. Infoodstuffs and food products, and so forth, once the cells of thematerial are destructed, dripping, which makes it difficult to restorethe organisms to the original state, occurs while the material isthawed.

Coarseness of the ice crystals is caused at freezing by a slowly passingthrough the range of ice crystallization temperature. Accordingly, inorder to prevent such coarseness of the ice crystals, the material to befrozen may be immersed in a liquid cooling medium or a liquid coolingmedium may be sprayed onto the material so that the material temperaturemay quickly passes through the range of ice crystallization temperaturesto cool the material rapidly. Although the process of immersing thematerial to be frozen into a liquid cooling medium or spraying a liquidcooling medium onto the material can cool the surface layer of thematerial quickly, a frozen layer is produced in the surface layer. Thecooling rate of the inner side of the frozen material is determined byheat transfer from the surface, so the frozen layer in the surface layerinterferes the heat transfer to the inner side, thus the cooling of theinner side of the frozen material is delayed. Consequently, thecoarseness of the ice crystals disadvantageously occurs in the inside ofthe frozen material; hence, the coarseness of the ice crystals is notprevented.

To solve the problem, a method for super-quickly cooling has beendisclosed in, for example, WO 01/24647 A1. This method has the step ofquickly freezing an object by lowering the ambient temperature of theobject to a temperature in the range of −30 to −100° C. while aunidirectional magnetic field is applied to the object or further thestep of cooling the object with cold air flow at 1 to 5 m/s and applyinga sound wave in the audio frequency band to the cold air flow, orfurther includes the step of applying an electric field to the object.

WO 01/24647 A1 also proposes a super-quickly freezing apparatus. Thisapparatus comprises a freezer capable of lowering its internaltemperature around the object to be freezed in the range of −30 to −100°C.; and magnetic field-generating means for applying a magnetic fieldfluctuating in one direction to the object, comprising static magneticfield-generating means and dynamic magnetic field-generating means.

According to the technique described in WO 01/24647 A1, the cells of thefrozen material are prevented from being destructed and the food afterthawing has a taste similar to its raw state. Thus, the quality of foodpreserved in frozen storage is fairly improved. In some types of food,however, the destruction of the cells cannot be completely preventedeven by this technique, and quality degradation occurs undesirably inthe food frozen. In addition, the inventor of the present inventionfound in the technique of WO 01/24647 A1 that the variable magneticfield is so nonuniform that the effect of the variable magnetic field isnot evenly exerted on the frozen material, and that a part of the frozenfood is degraded in quality.

In view of these problems, an object of the present invention is toprovide a high-functional freezing apparatus and a high-functionalfreezing method that allow any type of food product, foodstuff, andorganism without destruction of their cells to be preserved in frozenstorage.

Another object of the present invention is to provide a high-functionalfreezing apparatus containing means for simultaneously applying anelectric field of variable frequency and a uniform magnetic field tofood and organism cells, and a high-functional freezing method.

DISCLOSURE OF INVENTION

In order to accomplish these objects, the inventor of the presentinvention has conducted intensive research on a method for preventingthe destruction of cells in materials in freezing. As a result, theinventor discovered that it is effective in preventing the coarseness ofice crystals and the destruction of the cells to quickly cool themaximum ice crystallization temperature range, in which ice crystalsgrow at a high rate, and to suppress the nucleation of ice crystals. Theinventor also discovered through further continued research that,application of an oscillating electric field and/or magnetic field to anobject to be frozen suppress the nucleation of ice crystals, so thatsupercooling can be achieved without nucleation of ice crystals down to−10° C. In particular, the inventor has reached a conclusion that it iseffective in preventing the nucleation of ice crystals to apply anoscillating electric field of variable frequency in the range of 50 Hzto 5 MHz.

Furthermore, the inventor discovered that, by simultaneously applying anoscillating electric field and a magnetic field to the object, the freewater in the object hydrates with protein and carbohydrate, which areground substances in food and organisms, to change into bound waterforming molecules of hydrated higher order structures. Consequently, theinventor found that the free water is reduced, so that the probabilityof ice crystallization decreases. Thus, the nucleation of ice crystalscan further be prevented.

Under the idea that it is important to apply a strong, uniform variablemagnetic field to the object to be frozen in order to prevent thenucleation of ice crystals, the inventor has conducted intensiveresearch on variable magnetic field-generating means capable ofgenerating a strong, uniform variable magnetic field. The intensity of amagnetic field decreases in inverse proportion to the square of thedistance from a magnetic field source. The research has been conductedaccording to the concept of disposing a variable magnetic field sourceclose to an object to be frozen (hereinafter may be referred to as theobject) as much as possible in order to obtain a strong, uniformvariable magnetic field. As a result, the inventor found that it iseffective to dispose a plurality of variable magnetic field sources inparallel, in series, or crosswise along a holder holding the object soas to be across the holder or so as to surround or sandwich the holder.

The inventor also found that addition of ionic air flow to cold air forcooling the object accelerates heat transfer to remarkably increase thecooling rate of the object.

The present invention has been accomplished through continued researchaccording to the above-described findings.

The summary of the present invention is as follows:

(1) A high-functional freezing apparatus including a freezer; and atleast one means selected from the group consisting of oscillatingelectric field-generating means for applying an oscillating electricfield to an object or objects to be frozen accommodated in or beingconveyed in succession to an internal space of the freezer and magneticfield-generating means for applying a magnetic field to the object orthe objects.

(2) A high-functional freezing apparatus according to (1), in which theoscillating electric field has a variable frequency in the range of 50Hz to 5 MHz.

(3) A high-functional freezing apparatus according to (1) or (2), inwhich the magnetic field-generating means is at least one means selectedfrom the group consisting of static magnetic field-generating means forgenerating a static magnetic field and/or variable magneticfield-generating means for generating a variable magnetic field.

(4) A high-functional freezing apparatus according to (3), in which thestatic magnetic field-generating means is a permanent magnet.

(5) A high-functional freezing apparatus according to (3), in which thevariable magnetic field-generating means is a dielectric coil.

(6) A high-functional freezing apparatus according to (3), in which theintensity of the static magnetic field is in the range of 1 to 10,000Gauss and the intensity of the variable magnetic field is in the rangeof 1 to 1,000 Gauss.

(7) A high-functional freezing apparatus according to (4), in which thepermanent magnet is disposed on an external wall of the freezer or onthe rear side of a holder for holding the object and the dielectric coilis disposed so as to be across the holder, so as to sandwich or so as tosurround the holder, without blocking cold air.

(8) A high-functional freezing apparatus according to (3), in which thefreezer is of a rack-type batch-style, and the variable magneticfield-generating means comprises a plurality of electromagnetic coilunits that generate a variable magnetic field by passing an alternatingcurrent therethrough and each electromagnetic coil unit is disposed soas to be across or surround a holder for placing the object on orholding the object and the plurality of the coil units are arranged soas to be in parallel, in series, or crosswise to the rack-type holder.

(9) A high-functional freezing apparatus according to (3), in which thefreezer is of a tunnel-type, and the variable magnetic field-generatingmeans for applying a variable magnetic field to the objects beingconveyed by a net conveyer belt into and frozen in the internal closedspace of the freezer in succession is an apparatus for generating avariable magnetic field which comprises a plurality of electromagneticcoil units for generating the variable magnetic field by applying analternating current, wherein a pair of electromagnetic coil units isdisposed in such a manner that each electromagnetic coil unit of thepair is separated by the net conveyer belt for placing the objects on orholding the objects and a plurality of the pairs are arranged inparallel along the moving direction of the net conveyer belt.

(10) A high-functional freezing apparatus according to (3), in which thefreezer is of a spiral-type, and the variable magnetic field-generatingmeans for applying a variable magnetic field to the objects beingconveyed by a net conveyer belt into and frozen in the internal closedspace of the freezer in succession is an apparatus for generating avariable magnetic field which comprises a plurality of electromagneticcoil units for generating the variable magnetic field by applying analternating current, wherein a pair of electromagnetic coil units isdisposed in such a manner that each electromagnetic coil unit of thepair is separated by the net conveyer belt for placing the objects on orholding the objects and a plurality of the pairs are arranged inparallel along the moving direction of the net conveyer belt.

(11) A high-functional freezing apparatus according to any one of (8) to(10) in which each of the electromagnetic coil units comprises: a coilbase with a predetermined shape for forming a coil; an electromagneticcoil formed of a predetermined turns of highly conductive wire with aninsulative coating, wound around the coil base; and a caulking compoundsealing the electromagnetic coil.

(12) A high-functional freezing apparatus according to (11), in whichthe coil base comprises an electrically insulative, water-resistant,heat-resistant, and magnetically permeable material.

(13) A high-functional freezing apparatus according to (12), in whichthe material of the coil base is a plastic.

(14) A high-functional freezing apparatus according to any one of (1) to(13), in which the alternating electric field-generating means comprisesat least one pair of electrodes having electrodes opposing each other soas to be separate by the object and an oscillating electric fieldgenerator for applying an oscillating electric field between theelectrodes.

(15) A high-functional freezing apparatus according to (14), in whichthe electrodes comprises a sheet of a stainless steel or a steel platedwith silver or gold, having a plurality of protrusions.

(16) A high-functional freezing apparatus according to any one of (1) to(15), further comprises air blowing means for blowing cold air in thefreezer to the object and an ionic air generator for adding ionic air tothe cold air blown from the air blowing means.

(17) A high-functional freezing apparatus according to (16), in whichthe ionic air generator comprises a tubular anode, a linear cathodeentering into the inside of the tubular anode, and a voltage generatorfor applying a voltage between the anode and the cathode.

(18) A high-functional freezing apparatus according to (17), in whichthe tubular anode and the linear cathode are made of stainless steel orsteel plated with silver or gold.

(19) A high-functional freezing apparatus according to any one of (1) to(18), in which the surface of the inside wall of the freezing roomcomprise a material capable of absorbing far infrared rays.

(20) A high-functional freezing apparatus according to any one of (1) to(19), wherein a honeycomb formed of a highly heat-conductive material isprovided in a flow path of the cold air in the freezing room.

(21) A high-functional freezing apparatus according to any one of (1) to(20), in which the freezer is replaced with a refrigerator or arefrigerator-freezer so that the frozen object is allowed to be arefrigerated preserve or a fridge-frozen preserve.

(22) A high-functional freezing method in which an object accommodatedin an internal space of a freezer is quickly cooled to a predeterminedtemperature with an oscillating electric field and/or a alternatingmagnetic field applied while water is prevented from freezing, andsubsequently, the object is instantaneously frozen at the predeterminedtemperature to be preserved with the freshness maintained high.

(23) A high-functional freezing method according to (22), in which theoscillating electric field has a variable frequency in the range of 50Hz to 5 MHz.

(24) A high-functional freezing method according to (23), in which thefrequency is continuously varied.

(25) A high-functional freezing method according to (22), in which themagnetic field is a static magnetic field and/or a variable magneticfield.

(26) A high-functional freezing method according to (25), in which theintensity of the static magnetic field is in the range of 1 to 10,000Gauss and the intensity of the variable magnetic field is in the rangeof 1 to 1,000 Gauss.

(27) A high-functional freezing method according to (25), in which thevariable magnetic field is generated by applying an alternating currentto a plurality of electromagnetic coil units being disposed so as to beacross a holder or so as to surround or sandwich the holder holding theobject or on which the object is placed in the internal space of thefreezer, and being arranged in parallel, in series, or crosswise alongthe holder.

(28) A high-functional freezing method according to (27), in which eachof the electromagnetic coil units comprises: a coil base with apredetermined shape for forming a coil; an electromagnetic coil formedof a predetermined turns of highly conductive wire with an insulativecoating, wound around the coil base; and a caulking compound sealing theelectromagnetic coil.

(29) A high-functional freezing method according to any one of (22) to(28), in which ionic air is added to cold air in the freezer.

(30) A high-functional freezing methods according to any one of (22) to(29), wherein the surface of inside wall of the freezer comprise amaterial capable of absorbing far infrared rays.

(31) A high-functional freezing method according to any one of (22) to(30), in which the cold air in the freezer is passed through a highlyheat-conductive honeycomb.

(32) A uniform variable magnetic field generator which comprises amagnetic field generator contained in a freezing apparatus and avariable magnetic field generator having electromagnetic coil unitsthrough which an alternating current is passed to apply a variablemagnetic field to an object in a closed space, the electromagnetic coilunits being disposed so as to be able to apply the uniform variablemagnetic field to the object, in such a manner as to be across a holdfor placing the object on or holding the object, or as to around orsandwich the holder, and a plurality of electromagnetic coil units isarranged in parallel, in series, or crosswise along the holder.

(33) A uniform variable magnetic field generator according to (32), inwhich each of the electromagnetic coil units comprises: a coil base witha predetermined shape for forming a coil; an electromagnetic coil formedof a predetermined turns of highly conductive wire with an insulativecoating, wound around the base; and a caulking compound sealing theelectromagnetic coil.

(34) A uniform variable magnetic field generator according to (33), inwhich the coil base comprises an electrically insulative,water-resistant, heat-resistant, and magnetically permeable material.

(35) A uniform variable magnetic field generator according to (34), inwhich the material is a plastic.

(36) A uniform variable magnetic field generator according to any one of(32) to (35), in which the uniform variable magnetic field generatoroperates in a liquid of water, seawater, or alcohol.

(37) A uniform variable magnetic field generator according to any one of(32) to (36), in which the electromagnetic coil units are movablydisposed.

(38) A freezing apparatus including the uniform variable magnetic fieldgenerator as set forth in any one of (32) to (37).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic general representation of a high-functionalfreezing apparatus according to the present invention.

FIG. 2 is a schematic general sectional view of an ionic air flowgenerator according to the present invention.

FIG. 3 is a schematic general sectional view of a variable magneticfield generator according to the present invention.

FIG. 4 is a schematic general representation of a uniform variablemagnetic field generator according to the present invention.

FIG. 5 is a schematic general representation of a uniform variablemagnetic field generator according to the present invention.

FIG. 6 is a schematic general representation of a uniform variablemagnetic field generator according to the present invention.

FIG. 7 is a general representation of an electromagnetic coil unitsuitable for the uniform variable magnetic field generator of thepresent invention.

FIG. 8 is a schematic general sectional view of a freezing apparatusaccording to the present invention, including a uniform variablemagnetic field generator.

FIG. 9 is a schematic general sectional view of a freezing apparatusaccording to the present invention, including a uniform variablemagnetic field generator.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows a high-functional freezing apparatus according to thepresent invention.

The high-functional freezing apparatus of the present inventioncomprises a freezer 1; and oscillating electric field-generating means 3for applying an oscillating electric field to objects 2 to be frozenand/or magnetic field-generating means 6 for applying a magnetic fieldto the objects 2.

The oscillating electric field-generating means 3 comprises a pair ofelectrodes 3 a and 3 b opposing each other so as to sandwich the objects2; and an oscillating electric field generator 3 c for applying anoscillating electric field between the pair of electrodes 3 a and 3 b,thus applying the oscillating electric field 31 to the objects 2 throughthe pair of electrodes 3 a and 3 b. In the present invention,preferably, the oscillating electric field generator 3 c comprises afrequency generator to vary the frequency, and an amplifier circuit toapply an electric field with a desired intensity (100 to 5,000 V/cm) tothe pair of electrodes.

Although FIG. 1 shows only one pair of electrodes, it is preferable thatif the objects 2 accommodated in the internal space of the freezer 1 arepiled on, for example, a tray in at least two stacks in the heightdirection, the stacks are disposed between respective pairs ofelectrodes.

Any type of electrode may be used, but the electrode is preferably astainless steel or a steel plate plated with silver or gold from theviewpoint of uniformly applying an alternating electric field to theobjects, or of corrosion resistance and hygiene. It is also preferablethat the plate electrode has a plurality of protrusions from theviewpoint of electric energy release efficiency and applying a uniformelectric field.

In the present invention, preferably, the objects accomodated in theinternal space of the freezer are subjected to the application of anoscillating electric field from the oscillating electricfield-generating means to cool quickly to a predetermined temperaturewhile water is prevented from freezing, and are then frozeninstantaneously at the predetermined temperature with the stopping ofthe application of the oscillating electric field. The predeterminedtemperature is preferably in the range of −20 to −40° C.

In the present invention, preferably, the oscillating electric field tobe applied has a variable frequency in the range of 50 Hz to 5 MHz. Morepreferably, the variable frequency is 250 kHz and 3 MHz. In order toeliminate growing ice crystal nucleuses, the ice crystal nucleuses mustbe allowed to absorb a required electric field energy effectively. Theinventor found that such an effective electric field energy is in awavelength band at frequencies of particularly 250 kHz and 3 MHz.

When the object 2 to be frozen is cooled while an oscillating electricfield 31 with variable frequency is applied to the objects, theoscillating electric field acts on the growing ice crystal nucleuses inthe range of ice crystallization temperatures, thereby eliminating thegrowing ice crystal nucleuses. Thus, a supercooling state is achieved inwhich ice crystal nucleuses are prevented from being formed down to alow temperature of −10° C. or lower. In addition, suppressing icecrystallization prevents the surface of the object from freezing toallow the cold air to be transmitted to the inside of the object. Thus,the cooling rate of the objects is remarkably increased.

By applying an oscillating electric field to the objects, the objects,that is, any type of food and organisms, are preserved in frozen storagewith the cells prevented from being destructed.

It is effective that the oscillating electric field is applied bycontinuously scanning the objects with an electric field energy at afrequency in the range of 50 Hz to 5 MHz, or by varying the frequency instages (step by step). The temperature range of −2 to −10° C.particularly increases the electric field energy effective ineliminating the ice crystals at 250 kHz; and the temperature range of−30 to −60° C., at 3 MHz. Accordingly, it is also effective to apply anelectric field energy at a frequency of either 250 kHz or 3 MHzseparately.

The oscillating electric field generator 3 c used in the freezingapparatus of the present invention may control the frequency accordingto information from a temperature sensor.

In the present invention, the magnetic field-generating means 6 forapplying a magnetic field to the objects may be used instead of theabove-described oscillating electric field-generating means 3. This willproduce the same effect as above.

In the present invention, preferably, the magnetic field-generatingmeans 6 for applying a magnetic field to the objects is provided inaddition to the oscillating electric field-generating means 3. Bysimultaneously applying an oscillating electric field and a magneticfield to the objects, the free water in the objects hydrates withprotein and carbohydrate, which are ground substances in food ororganisms, to change into bound water forming molecules of hydratedhigher order structures. Consequently, the free water is reduced, sothat the probability of ice crystallization decreases. Thus, thenucleation of ice crystals can further be prevented. Thus, the cold aircan be transmitted into the inside of the objects effectively and,accordingly, the cooling rate of the objects is remarkably increased.

In the present invention, preferably, the magnetic field-generatingmeans 6 comprises static magnetic field-generating means 6 a forgenerating a static magnetic field and variable magneticfield-generating means 6 b for generating a variable magnetic field.Preferably, the static magnetic field-generating means 6 a is a set ofpermanent magnets and the variable magnetic field-generating means 6 bis a dielectric coil.

Preferably, the permanent magnets serving as the static magneticfield-generating means 6 a are disposed on a sidewall of the freezer 1with the polarities aligned so that a static magnetic field acts on theobjects 2 placed in the internal space of the freezer. FIG. 1 shows thatthe static magnetic field-generating means 6 a is disposed on thesidewall of the freezer 1 with the polarities aligned so that the staticmagnetic field is applied in the vertical direction, the direction ofthe static magnetic field may of course be oriented in the horizontaldirection. Preferably, the static magnetic field has an intensity in therange of 1 to 10,000 Gauss. In the case of a static magnetic fieldintensity of less than 1 Gauss, the effect of the static magnetic fieldis not obvious due to the influence of geomagnetism. On the other hand,in view of a manufacturing possibility of the permanent magnet, theupper limit of the static magnetic field is preferably 10,000 Gauss. Thepermanent magnets serving as the static magnetic field-generating means6 a may be disposed on the backside of a holder 21 for holding theobjects 1 with the polarities aligned so that the static magnetic fieldacts on the objects 1. The holder 21 for holding the objects 2 may be,for example, a tray, a net, or a belt.

The dielectric coil serving as variable magnetic field-generating means6 b provides a variable magnetic field whose direction is variedperiodically by passing an alternating current with a constant frequencythrough the coil. The alternating current passing through the dielectriccoil preferably has a commercial frequency in the range of 50 to 60 Hz.The intensity of the variable magnetic field is preferably in the rangeof 1 to 1,000 Gauss in consideration of proper intensity for each typeof object. While a variable magnetic field intensity of less than 1Gauss does not produce an effect distinguishable from that ofgeomagnetism, an intensity of more than 1,000 Gauss makes the apparatusexpensive and, thus, brings about an economical problem.

The dielectric coil may be disposed on the sidewall of the freezer.Alternatively, the dielectric coil may be disposed closer to the object2 so that the variable magnetic field acts on the objects effectively insuch a manner as to be across the holder holding the object 2 or as tosandwich or surround the holder, without blocking the cold air.

If the dielectric coil surrounds the holder holding the object 2,preferably, the dielectric coil 6 b is provided in such a manner thatthe winding of the dielectric coil surrounds the object 2 and the holderso that the flow of the cold air is not interrupted, as shown in FIGS. 1and 3. By disposing the dielectric coil 6 b closer to the objects 2, asshown in FIGS. 1 and 3, a variable magnetic field can act on the objectsuniformly and effectively and, consequently, the nucleation of icecrystals can further be prevented.

Although the dielectric coil is disposed so that the variable magneticfield acts on the objects horizontally in FIGS. 1 and 3, it is notlimited to this. It goes without saying that the variable magnetic fieldmay be applied in a direction parallel to or perpendicular to the staticmagnetic field.

In the present invention, in order to prevent the destruction of theobject cells, the above-described oscillating electric field and/or thevariable magnetic field are applied to the objects so as to suppress thenucleation of ice crystals. In addition, it is preferable to quicklylower temperature so as to pass through a maximum ice crystallizationtemperature range in which coarse ice crystals are produced at a highrate. For this purpose, an ionic air generator 4 is preferably providedto add ionic air to the cold air for cooling the objects. The ionic airgenerator may be disposed in any location as long as the cold air forcooling the objects can circulate.

The cold air for cooling the objects is generated by freezing means 5and supplied to the objects 2 by air blowing means 55 provided insidethe freezer 1. In the present invention, preferably, ionic airconstituted of negative air ions, generated by the ionic air generator 4is added to the cold air blown from the air blowing means 55. Bysupplying the cold air containing the ionic air, direct heat transfer tothe objects is accelerated and, thus, heat is absorbed from the objectsto promote rapid decrease in temperature of the objects.

Preferably, the cold air supplied to the objects 2 from the air blowingmeans 55 has a wind velocity of 1 to 5 m/s from the viewpoint ofpromoting convection heat transfer. A wind velocity of less than 1 m/sof the cold air leads to convection heat transfer insufficient to ensurerapid decrease in temperature. In contrast, a wind velocity of more than5 m/s of the cold air vaporizes a water layer produced on the surfacesof the objects. Thus, the objects become liable to be oxidized.

The ionic air generator 4 preferably includes a tubular anode 4 a, alinear cathode 4 b entering into the inside of the tubular anode 4 a,and a voltage generator 4 c for applying a voltage between the anode 4 aand the cathode 4 b, as shown in FIG. 2.

The voltage applied between the anode and the cathode is preferably10,000 V/cm or less, and more preferably 7,000 V/cm or less. Thus, thecold air (air) is ionized into negative ions at the cathode. Since thenegative ions are drawn to the anode, the other air not ionized is alsodrawn together and, thus ionic air is generated.

In the ionic air generator 4 of the present invention, preferably, thetubular anode 4 a and the linear cathode 4 b entering into the inside ofthe anode are used in combination. Thus, the ionic air is efficientlyadded to the cold air.

Preferably, the tubular anode 4 a and the linear cathode 4 b are formedof the same material, and more preferably of a stainless steel or asteel plated with silver or gold, from the viewpoint of corrosionresistance and hygiene.

In the present invention, the freezing means 5 for generating cold airuses a conventionally known freezing cycle that includes a compressor53, a condenser 54, an expansion valve 52, and a cooling pipe(evaporator) 51 that are combined in series so as to circulate a coolingmedium. The expansion valve 52 and the cooling pipe (evaporator) 51 aredisposed in the internal space of the freezer 1 to contribute togenerating cold air.

In the present invention, preferably, the internal wall surfaces of thefreezer are constituted of a material capable of absorbing far infraredrays so as to help temperature of the object decrease quickly. In thepresent invention, the material capable of absorbing for infrared raysmay be applied onto the internal walls as a coating, or a plate formedof the material may be disposed on the internal walls. Thus, radiantheat (far infrared rays) from the objects is rapidly absorbed to helpthe temperature of the objects decrease quickly. The material capable ofabsorbing far infrared rays absorbs heat of the objects in proportion tothe fourth power of the difference ΔT in temperature between the objectsand the internal walls, thus greatly contributing to rapid cooling ofthe objects. The material capable of absorbing far infrared rays, in thepresent invention, refers to a material having an absorptance of 95% ormore for far infrared rays in the wavelength band of 5 to 1,000 μm. Forexample, a ceramic, such as silica, alumina, or iron oxide, may be used.

In addition, preferably, a highly heat-conductive honeycomb 56 isprovided in the flow path of the cold air in the freezer. By introducingcold air into the honeycomb 56, the decrease in temperature of the coldair and the uniformization of the cold air flow can be promoted.Although the structure of the honeycomb 56 is not particularly limitedas long as cold air can pass through it, it is preferable that thehoneycomb has a grid-like section and allows the air to pass through inthe longitudinal direction. Also, although the location of the honeycombis not particularly limited as long as the honeycomb is disposed in theflow path of the cold air, it is preferable that the honeycomb isdisposed at the outlet side of the ionic air generator 4, that is, atthe downstream side of the cold air flow path, as shown in FIG. 1, fromthe viewpoint of providing cold air whose temperature is more uniformlylowered. The highly heat-conductive material of the honeycomb ispreferably a stainless steel. Preferably, the dimensions of thehoneycomb are appropriately determined according to the dimensions ofthe freezer.

It goes without saying that a heat insulator is provided between theexternal walls and the internal walls of the freezer 1 though FIG. 1does not show the heat insulator.

The freezing apparatus shown in FIG. 1 is of a rack type, but notlimited to this. It goes without saying that a conventional freezingapparatus, such as of tunnel type or spiral type, may be used.

In the present invention, preferably, the foregoing dielectric coil isreplaced with a uniform variable magnetic field generator including aplurality of electromagnetic coil units 61 as the variable magneticfield generating means 6 b.

Each electromagnetic coil unit 61 comprises a coil base 611 having apredetermined shape and an electromagnetic coil 612 formed of apredetermined turns of a highly conductive wire 612 a with an insulativecoating, wound around the coil base 611. The electromagnetic coil 612 issealed with a caulking compound 613. Preferably, the coil base has acase-like section so as to house the electromagnetic coil. The coil basehaving the case-like section, accomodating the electromagnetic coilsealed with the caulking compound 613 is provided with a cover formed ofthe same material, which is bonded to the coil base with an adhesive orthe like. Thus, the electromagnetic coil unit 61 containing theelectromagnetic coil 612 is completed.

Preferably, the coil base 611 is formed of an electrically insulative,water-resistant, heat-resistant, and magnetically permeable material.Preferred materials include plastics, rubber, wood, and their composite.

The coil base 611 having the case-like section preferably has apredetermined shape according to the holder for placing the object on orholding the objects, but is not particularly limited. If the holder isof a rack type, a rectangular or square ring is preferable; if theholder is of a net belt conveyor type, a rectangular or square ring ispreferable.

The highly conductive wire is, for example, a single or stranded Cu wire(copper wire). The highly conductive wire wound around the coil base toserve as the electromagnetic coil is coated with a highly electricallyinsulative film. Exemplary highly electrically insulative coatingincludes polyimide resin, nylon, and polytetrafluoroethylene (tradename: Teflon).

FIG. 4 schematically shows an example of the electromagnetic coil unit61 using a rectangular ring-shaped base. A variable magnetic field isgenerated by applying alternating current to the electromagnetic coilunits 61 having the above-described structure. However, it goes withoutsaying that the present invention does not limit the form of the coilunit to this. Preferably, the intensity of the variable magnetic fieldis set at a desired level according to the magnitude of alternatingcurrent applied to the coil, the number of turns of the coil, and otherfactors.

The uniform variable magnetic field generator of the present inventionhas, preferably, the foregoing electromagnetic coil units 61, andalternating current is applied to the electromagnetic coil units togenerate a variable magnetic field, thereby applying a uniform variablemagnetic field to the objects in a closed space. It goes without sayingthat the variable magnetic field generator includes alternatingcurrent-applying means 61 a for applying an alternating current to theelectromagnetic coil units though the description is omitted.

In the uniform variable magnetic field generator of the presentinvention, the electromagnetic coil units 61 are disposed in the closedspace 7 so as to uniformly apply a variable magnetic field to theobjects, in such a manner as to be across the holder 21 holding theobjects 2 or on which the object 2 is placed, or as to surround orsandwich the holder 21. The plurality of electromagnetic coil units 61are also arranged in parallel, in series, or crosswise along the holder21. By using the plurality of electromagnetic coil units 61, a variablemagnetic field with a uniform intensity can be provided, and thevariable magnetic field with the uniform intensity can be applied to theobjects.

It is preferable that the number of and the intervals between theelectromagnetic coil units 61 are appropriately set according to thelength of the holder, the uniformity of the magnetic field intensity,and so forth.

The uniform variable magnetic field generator can operate in water,seawater, and other liquid, such as alcohol, as well as in the airbecause of the use of the electromagnetic coil units hermeticallycontaining the electromagnetic coil 612.

Preferably, in the uniform variable magnetic field generator, theelectromagnetic coil units 61 are disposed movably. The movably arrangedelectromagnetic coil units 61 can easily adapt to the variations oftype, shape, and arrangement of the objects.

FIGS. 4 and 5 show examples of the uniform variable magnetic fieldgenerator of the present invention.

In FIG. 4, the holder 21 for placing the objects 2 on or holding theobjects 2 is of a rack-type tray. In FIG. 4, three electromagnetic coilunits 61 are arranged in parallel along the holder 21, that is, therack-type tray 211, in such a manner as to surround the holder 21.

In FIG. 5, the holder 21 for placing the objects 2 on or holding theobjects 2 is of a net belt conveyor 212. In FIG. 5, the electromagneticcoil units 61 are arranged in such a manner as to sandwich the holder21.

In FIG. 5, five pairs of rectangular ring-shaped electromagnetic coilunits 61 are arranged in parallel along the holder 21 or net beltconveyor 212 in such a manner that each pair of the electromagnetic coilunits 61 is separated above and below by the holder 21 or net beltconveyor 212. It goes without saying that each electromagnetic coil unitis connected to the alternating current-applying means 61 a though thefigures do not show it.

Even when the holder 21 is of the net belt conveyor 212, theelectromagnetic coil units 61 may be disposed at only one side of thenet belt conveyor such as to be across or cover the net belt conveyor,for applying a variable magnetic field to the objects.

By applying an alternating current to the electromagnetic coils 612 ofthe electromagnetic coil units 61 from the alternating current-applyingmeans 61 c, a variable magnetic field is generated. The variablemagnetic fields in FIGS. 4 and 5 are generated respectively parallel andperpendicular to the holder to apply a uniform variable magnetic field.While FIGS. 4 and 5 show the electromagnetic coil units disposed inparallel along the holder 21, the electromagnetic coil units may bedisposed in series or crosswise. It goes without saying that this isdifferent in only the direction in which the magnetic field is appliedto the objects and that perfectly the same effects are produced by theapplication of a variable magnetic field.

The “closed space” in the present invention may be, for example, afreezer, a refrigerator, or a refrigerator-freezer.

The uniform variable magnetic field generator of the present invention,including the above-described electromagnetic coil units is incorporatedwith a common freezer or any other special freezer and, thus, can bebroadly used.

A freezing apparatus containing a uniform variable magnetic fieldgenerator having the above-described structure of the present inventionwill now be described. The freezing apparatus referred to in the presentinvention may include a freezing apparatus, a refrigerating apparatus,or a refrigerate-freezing apparatus.

The freezing apparatus of the present invention comprises a freezer 1and a variable magnetic field generator for applying a variable magneticfield to objects 2 to be frozen accomodated in the internal closed spaceof the freezer 1. In the present invention, the variable magnetic fieldgenerator is a uniform variable magnetic field generator including aplurality of electromagnetic coil units 61 that generates a variablemagnetic field by applying an alternating current. The electromagneticcoil units 61 has the above-described structure, and is disposed in sucha manner as to be across the holder 21, which holds the objects 2 or onwhich the objects 2 are placed, or as to surround or sandwich the holder21. The plurality of electromagnetic coil units 61 are arranged inparallel, in series, or crosswise to a holder 21. The electromagneticcoil units thus disposed apply a variable magnetic field with a uniformintensity to the objects.

If the freezer is of rack-type batch-type, preferably, theelectromagnetic coil units 61 are disposed, so as to across therack-type holder 21, or the rack-type tray 211, which holds the objects2 or on which the objects are placed, as shown in FIGS. 4 and 8, or soas to surround the rack-type holder or rack-type tray 211, which holdsthe objects or on which the object are placed. Further the plurality ofelectromagnetic coil units 61 are arranged in parallel along therack-type holder. Alternatively, the plurality of electromagnetic coilunits may be arranged in series or crosswise.

The electromagnetic coil units thus disposed apply a variable magneticfield with a uniform intensity in the horizontal direction to theobjects.

FIG. 5 shows a tunnel-type freezer in which the objects are continuouslyconveyed into the internal closed space of the freezer one after anotherby a net conveyor belt to be accommodated and frozen. In this instance,preferably, each electromagnetic coil unit 61 of pairs are disposedabove and below the holder 21, that is net conveyor belt 212, holdingthe objects 2 so that each pair is separated by the holder, and thepairs of the electromagnetic coil units are disposed in parallel in themoving direction of net conveyor belt. The electromagnetic coil unitsthus disposed apply a variable magnetic field with a uniform intensityin the vertical direction to the objects to be frozen.

FIG. 6 shows a spiral-type freezer in which the objects are continuouslyconveyed into the internal closed space of the freezer one after anotherby a net conveyor belt to be accommodated in a spiral manner and to befrozen while being conveyed upward. In this instance, preferably, pairsof the rectangular ring-shaped electromagnetic coil units 61 aredisposed in parallel along the holder 21, that is net conveyor belt 212,in the moving direction of the net conveyor belt 212 so that each memberof a pair is separated by the net conveyor belt 212 holding the objects2. By applying an alternating current to the electromagnetic coil unitsthus disposed, a variable magnetic field with a uniform intensity isapplied to the objects to be frozen.

It goes without saying that the freezing apparatus of the presentinvention includes freezing means 5 for generating cold air for coolingthe objects 2 housed in the internal space of the freezer and airblowing means 55 for supplying the cold air to the objects provided inthe freezer, as shown in FIG. 8, in addition to the above-describedfreezer 1 and variable magnetic field-generating means 6 b. It goeswithout saying that a heat insulator is provided between the externalwalls and the internal walls of the freezer 1 though the figures do notshow the heat insulator.

The freezing means 5 uses any known freezing cycle including acompressor 53, a condenser 54, an expansion valve 52, and a cooling pipe(evaporator) 51 that are combined in series so as to circulate a coolingmedium. The expansion valve 52 and the cooling pipe (evaporator) 51 aredisposed in the internal space of the freezer 1 to contribute togenerating cold air. Preferably, the internal wall surfaces of thefreezer are constituted of a material capable of absorbing far infraredrays so as to help the object temperature decrease quickly. The materialcapable of absorbing far infrared rays may be applied onto the internalwalls as a coating, or a plate formed of the material may be disposed onthe internal walls. Thus, radiant heat (far infrared rays) from theobjects is rapidly absorbed to help the temperature of the objectsdecrease quickly. The material capable of absorbing far infrared raysabsorbs heat of the objects in proportion to the fourth power of thedifference ΔT in temperature between the objects and the internal walls,thus greatly contributing to rapid cooling of the objects.

Ionic air constituted of negative air ions, generated by the ionic airgenerator 4 may be added to the cold air blown from the air blowingmeans 55, as shown in FIG. 9. By supplying the cold air containing theionic air, direct heat transfer to the objects is accelerated and, thus,heat is absorbed from the objects to promote rapid decrease intemperature of the objects. Preferably, a highly heat-conductivehoneycomb 56 is further provided in the flow path of the cold air in thefreezer, as shown in FIG. 9. By introducing cold air into the honeycomb56, the decrease in temperature of the cold air and the uniformizationof the cold air flow can be promoted.

It goes without saying that the freezing apparatus of the presentinvention may include static magnetic field-generating means 6 a forgenerating a static magnetic field in addition to the foregoing variablemagnetic field generator.

Furthermore, it is preferable that the freezing apparatus furtherinclude oscillating electric field-generating means for applying anoscillating electric field to the objects though it is not particularlyshown in the figures.

EXAMPLES Example 1

In use of the rack-type freezer shown in FIG. 1 being thehigh-functional freezing apparatus of the present invention, raw chickenmeat and tuna fish placed as the objects 2 on the holder 21 andaccomodated in the internal space of the freezer 1 were frozen by beingsubjected to the action of the freezing means 5. The internal walls ofthe freezer 1 were provided with a material capable of absorbing farinfrared rays, silica-alumina-iron oxide ceramic in this example. Thespecifications of the freezing apparatus used were: dimensions, 1.5 m inheight by 1.5 m in width by 2.5 m in length; freezing compressor, 10 HP;cooling medium, R22.

For freezing, the oscillating electric field-generating means 3 appliedan oscillating electric field; further a permanent magnet serving as thestatic magnetic field-generating means 6 a and a dielectric coil servingas the variable magnetic field-generating means 6 b applied a staticmagnetic field and a variable magnetic field; further the ionic airgenerator 4 added ionic air to cold air; or further cold air was passedthrough the honeycomb with a grid-like section, having a bore size of10×10 mm and a length of 100 mm. The holder 21 holding the objects 2 wasdisposed between the electrodes of the oscillating electricfield-generating means, as shown in FIG. 1.

A stainless steel plates with protrusions of 3 mm in height at intervalsof 10 mm were used as the electrodes of the alternating electricfield-generating means 3. The ionic air generator 4 included a stainlesssteep pipe (20 mm in diameter by 50 mm in length) as an anode and astainless steel wire of 0.5 mm in diameter as a cathode, and a voltageof 5,000 V/cm was applied to generate ionic air.

The alternating electric field were applied in three ways: (1) electricfield energy of a frequency of 250 kHz; (2) electric field of afrequency of 3 MHz; and (3) electric field energy of frequenciescontinuously varied in the range of 50 Hz to 5 MHz. The intensity of theelectric field was set at 150 V/cm; the distance between the electrodes,100 mm.

For comparison, freezing without application of any oscillating electricfield was performed. The conditions of the electric field, magneticfield, and ionic air applied to the objects are shown in Table 1.

In freezing, the targeted central temperature of the objects was set at−20° C. and −40° C. The central temperature of the objects was measuredwith a thermocouple. Time required to cool the central temperature from0° C. to −20° C. or −40° C. was compared with the time required forconventional quick freezing to evaluate the freezing ability. Withreference to the time for the conventional quick freezing, the time forcooling the central temperature from 0° C. to −20° C. or −40° C. wasexpressed as: “Δ” when the time was the same as the reference; “□” whenthe time was 1% to 20% reduced; “◯” when the time was 20% to 50%reduced; and “⊚” when the time was 50% or more reduced.

After being stored at the temperature for three months, the frozenobjects were thawed under running water of 10° C., and were subjected toquality test.

The quality was determined to be: “⊚” when the cells were not destructedwith the same color, flavor, and taste as the original raw food; “◯”when the cells were hardly destructed with color, flavor, and tastesimilar to those of the original raw food; “□” when the cells wereslightly destructed, but dripping was reduced with good taste; “X” whenthe cells were destructed with a lot of dripping and degraded color,flavor, and taste.

The total evaluation was expressed as bad (X), good (□), very good (◯),or excellent (⊚).

The results are shown in Table 1.

The cells of all the samples according to the present invention were notdestructed, and the taste was not degraded at all. In contrast, thecells of the samples of the comparative example, in which no oscillatingelectric field was applied, were destructed, and the taste was degraded.The present invention produced the same effect in other fisheryproducts, raw meats, and other food products, in addition to the chickenand tuna fish.

TABLE 1 Freezing conditions Magnetic field Oscillating electric Variablemagnetic field field Electric Static Magnetic field magnetic field FarFreezing intensity Frequency field Frequency intensity Ionic infraredNo. No. Electrode* V/cm Hz Gaus Hz Gauss air Honeycomb absorber  1 AStainless 150 50 Hz to — — — — — — 3 MHz  2 B Stainless 150 250 KHz — —— — — —  3 C Stainless 150 3 MHz — — — — — —  4 D Stainless 150 250 KHz— — — Used — —  5 E Stainless 150 250 KHz — — — — Used —  6 F Stainless150 250 KHz — — — — — Used  7 G Stainless 150 250 KHz — — — Used UsedUsed  8 H Stainless 150 250 KHz 10 50 5 Used Used Used  9 I Stainless150 3 MHz 10 50 5 Used Used Used 10 J Stainless 150 50 Hz to 10 50 5Used Used Used 5 MHz 11 K Stainless 150 50 Hz to — 50 5 Used Used Used 5MHz 12 M — — — — — — — — — 13 N — — — — — — — — Used Freezing timeRelative Relative time for time for cooling the cooling the centralcentral temperature temperature Frozen object quality EvaluationFreezing from 0° C. to from 0° C. to Species Total No. −20° C. −40° C.Chicken Tuna evaluation Remark  1 ο ο ο ο ο Example  2 ο ο ο ο ο Example 3 ο ο ο ο ο Example  4 ο ο ο ο ο Example  5 ο ο ο ο ο Example  6 ο ο οο ο Example  7 ο ο ο ο ο Example  8 ⊚ ⊚ ⊚ ⊚ ⊚ Example  9 ⊚ ⊚ ⊚ ⊚ ⊚Example 10 ⊚ ⊚ ⊚ ⊚ ⊚ Example 11 ⊚ ⊚ ⊚ ⊚ ⊚ Example 12 Δ Δ X X XComparative example 13 □ □ □ □ □ Comparative example *Stainless,stainless steel plate electrode with protrusions

Example 2

A variable magnetic field was generated with a uniform variable magneticfield generator including the electromagnetic coil units 61 disposed inparallel in the longitudinal direction of the rack-type holder 211, asshown in FIG. 4. Four electromagnetic coil units 61 were disposed inparallel in the longitudinal direction of the rack-type holder 211. Eachelectromagnetic coil unit 61 comprised a rectangular ring-shaped plasticbase 611 of 1.2 m in length by 0.7 m in width, having a case-like,U-shaped section with a bore-size of 4 cm×4 cm and an electromagneticcoil 612 formed of 600 turns of copper wire 612 a coated with apolyimide resin, wound around the coil base. The electromagnetic coil612 was subjected to caulking. Then, a cover was bonded to thecase-shaped base with an adhesive and, thus, the electromagnetic coilunit containing the electromagnetic coil was completed.

A coil current of 1 A being an alternating current with a commercialfrequency of 50 Hz was passed through the electromagnetic coil units 61from the alternating current-applying means 61 a to generate a variablemagnetic field. The intensities of the magnetic field at several pointson the rack-type holder 21 were measured to evaluate the uniformity ofthe magnetic field. For the measurement of the magnetic field intensity,a gauss meter was used. As a result, it has been shown that the magneticfield intensity on the rack-type holder 211 was in the range of 5 to 7Gauss, being hardly varied and that a uniform magnetic field can beapplied to the objects.

Objects were frozen as in Example 1 using a freezing apparatus shown inFIG. 9, including the above-described uniform variable magnetic fieldgenerator. After being stored for three months at the temperature atwhich the objects were frozen, the frozen objects were thawed underrunning water of 10° C., and were subjected to quality test with thesame reference as in Example 1.

The results are shown in Table 2. In addition, freezing with applicationof oscillating electric field, not shown in FIG. 9, was also performed.

According to the present invention, the cells of food were notdestructed and the taste was not degraded at all.

TABLE 2 Freezing conditions Alternating electric Magnetic field fieldVariable magnetic field Electric Static Magnetic field magnetic fieldFar Freezing intensity Frequency field Frequency intensity Ionicinfrared No. No. Electrode* V/cm Hz Gauss Type Hz Gauss air Honeycombabsorber 21 P — — — — FIG. 4 50 5 to 7 Used Used Used 22 Q — — — 10 FIG.4 50 5 to 7 Used Used Used 23 R Stainless 150 50 Hz to 10 FIG. 4 50 5 to7 Used Used Used  5 MHz Freezing time Relative Relative time for timefor cooling the cooling the central central temperature temperatureFrozen object quality Evaluation Freezing from 0° C. to from 0° C. toSpecies Total No. −20° C. −40° C. Chicken Tuna evaluation Remark 21 ο οο ο ο Example 22 ο [ ο ο ο Example 23 ⊚ ⊚ ⊚ ⊚ ⊚ Example *Stainless,stainless steel plate electrode with protrusions

Example 3

A variable magnetic field was generated with a uniform variable magneticfield generator including a plurality of electromagnetic coil units 61disposed in parallel in the moving direction of the holder (net conveyerbelt 212), as shown in FIG. 5. Electromagnetic coil units 61 weredisposed above and below the net conveyer belt 212 of 1 m in width by 10m in length so that each member of a pair of the electromagnetic coilunits is separated by the net conveyer belt 212 with a distance of 10 cmfrom the net conveyer belt 212. Forty pairs of electromagnetic coilunits 61 were disposed along the moving direction of the net conveyerbelt 212 at intervals of 20 cm. Each electromagnetic coil unit 61comprised a rectangular ring-shaped coil base made by plastics of 1.0 min length by 0.6 m in width, having a thickness of 4 cm and anelectromagnetic coil formed of 600 turns of copper wire coated with apolyimide resin, wound around the coil base. The electromagnetic coilswere subjected to caulking.

A coil current of 1 A being an alternating current with a commercialfrequency of 50 Hz was passed through the electromagnetic coil units 61from the alternating current-applying means 61 a to generate a variablemagnetic field. The intensities of the magnetic field at several pointson the net conveyer belt 212 were measured to evaluate the uniformity ofthe magnetic field, as in Example 1. As a result, it has been shown thatthe magnetic field intensity on the net conveyer belt 212 was in therange of 5 to 7 Gauss with small variation, and that a uniform magneticfield can be applied to the objects.

Example 4

A variable magnetic field was generated in the spiral-type freezer shownin FIG. 6 with a uniform variable magnetic field generator including aplurality of electromagnetic coil units 61 disposed in parallel in themoving direction of the net belt conveyer 212. Electromagnetic coilunits 61 were disposed above and below the net belt conveyer 212 (15 cmin width by 10 m in length) so that each member of a pair of theelectromagnetic coil units is separated by the net belt conveyer 212with a distance of 10 cm from the net bet conveyer. Forty pairs ofelectromagnetic coil units 61 were disposed along the moving directionof the net belt conveyer 212 at intervals of 20 cm. Each electromagneticcoil unit 61 comprised a rectangular ring-shaped coil base made byplastics of 10 cm in length by 50 cm in width, having a thickness of 2cm and an electromagnetic coil formed of 600 turns of copper wire coatedwith a polyimide resin, wound around the coil base. The electromagneticcoils were subjected to caulking.

A coil current of 1 A being an alternating current with a commercialfrequency of 50 Hz was passed through the electromagnetic coil units 61from the alternating current-applying means 61 a to generate a variablemagnetic field. The intensities of the magnetic field at several pointson the net conveyer belt 212 were measured to evaluate the uniformity ofthe magnetic field, as in Example 1. As a result, it has been shown thatthe magnetic field intensity on the net conveyer belt 212 was in therange of 5 to 7 Gauss with small variation, and that a uniform magneticfield can be applied to the objects.

INDUSTRIAL APPLICABILITY

As described in detail above, the present invention promotes convectionheat transfer to achieve quick freezing and, further, suppress thenucleation of ice crystals down to a low temperature to achieveinstantaneous freezing. Thus, the present invention makes possible moreefficient high-functional freezing to freeze and preserve any type offood products, foodstuffs, and organisms without destructing theircells, thus producing an especial industrial effect.

Furthermore, the present invention allows a variable magnetic field witha uniform intensity to be applied to an objects to be frozen orsubjected to other treatment, accommodated in a closed space, such as afreezer. Thus, high-functional freezing is still more efficientlyachieved.

1. A high-functional freezing apparatus comprising: a freezer;oscillating electric field-generating means for applying an oscillatingelectric field to an object or objects to be frozen accommodated in orbeing conveyed in succession to an internal space of the freezer; andmagnetic field-generating means for applying a magnetic field to theobject or the objects, wherein, the oscillating electric field has oneof i) a variable frequency which varies continuously in the range of 50Hz to 5 MHz, ii) a variable frequency which varies in stages, step bystep, in the range of 50 Hz to 5 MHz, and iii) an alternativeoscillating frequency of 250 KHz or 3 MHz, and the freezing apparatus ishigh-functional by being configured to freeze and preserve any type offood products, food stuffs, and organisms without destructing theircells.
 2. A high-functional freezing apparatus according to claim 1,wherein the magnetic field-generating means is at least one meansselected from the group consisting of static magnetic field-generatingmeans for generating a static magnetic field and variable magneticfield-generating means for generating a variable magnetic field.
 3. Ahigh-functional freezing apparatus according to claim 2, wherein thestatic magnetic field-generating means is a permanent magnet.
 4. Ahigh-functional freezing apparatus according to claim 2, wherein thevariable magnetic field-generating means is an electromagnetic coil. 5.A high-functional freezing apparatus according to claim 2, wherein, themagnetic field-generating means comprises i) the static magneticfield-generating means for generating the static magnetic field with anintensity of the static magnetic field in the range of 1 to 10,000Gauss, and ii) the variable magnetic field-generating means forgenerating the variable magnetic field with an intensity of the variablemagnetic field in the range of 1 to 1,000 Gauss.
 6. A high-functionalfreezing apparatus according to claim 3, wherein the permanent magnet isdisposed on an external wall of the freezer or on the rear side of aholder for holding the object and the electromagnetic coil is disposedso as to be across the holder, so as to sandwich or so as to surroundthe holder, without blocking cold air.
 7. A high-functional freezingapparatus according to claim 2, wherein the freezer is of a rack-typebatch-style, and the variable magnetic field-generating means comprisesa plurality of electromagnetic coil units that generate a variablemagnetic field by passing an alternating current therethrough and eachelectromagnetic coil unit is disposed so as to be across or surround aholder for placing the object on or holding the object and the pluralityof the coil units are arranged so as to be in parallel, in series, orcrosswise to the rack-type holder.
 8. A high-functional freezingapparatus according to claim 2, wherein the freezer is of a tunnel-type,and the variable magnetic field-generating means for applying a variablemagnetic field to the objects being conveyed by a net conveyer belt intoand frozen in the internal closed space of the freezer in succession isan apparatus for generating a variable magnetic field which comprises aplurality of electromagnetic coil units for generating the variablemagnetic field by applying an alternating current, wherein a pair ofelectromagnetic coil units is disposed in such a manner that eachelectromagnetic coil unit of the pair is separated by the net conveyerbelt for placing the objects on or holding the objects and a pluralityof the pairs are arranged in parallel along the moving direction of thenet conveyer belt.
 9. A high-functional freezing apparatus according toclaim 2, wherein the freezer is of a spiral-type, and the variablemagnetic field-generating means for applying a variable magnetic fieldto the objects being conveyed by a net conveyer belt into and frozen inthe internal closed space of the freezer in succession is an apparatusfor generating a variable magnetic field which comprises a plurality ofelectromagnetic coil units for generating the variable magnetic field byapplying an alternating current, wherein a pair of electromagnetic coilunits is disposed in such a manner that each electromagnetic coil unitof the pair is separated by the net conveyer belt for placing theobjects on or holding the objects and a plurality of the pairs arearranged in parallel along the moving direction of the net conveyerbelt.
 10. A high-functional freezing apparatus according to claim 7,wherein each of the electromagnetic coil units comprises: a coil basewith a predetermined shape for forming a coil; an electromagnetic coilformed of a predetermined turns of highly conductive wire with aninsulative coating, wound around the coil base; and a caulking compoundsealing the electromagnetic coil.
 11. A high-functional freezingapparatus according to claim 10, wherein the coil base comprises anelectrically insulative, water-resistant, heat-resistant, andmagnetically permeable material.
 12. A high-functional freezingapparatus according to claim 11, wherein the material of the coil baseis a plastic.
 13. A high-functional freezing apparatus according toclaim 1, wherein the alternating electric field-generating meanscomprises at least one pair of electrodes having electrodes opposingeach other so as to be separated by the object and an oscillatingelectric field generator for applying an oscillating electric fieldbetween the electrodes.
 14. A high-functional freezing apparatusaccording to claim 13, wherein the electrodes comprise a sheet of astainless steel or a steel plated with silver or gold, having aplurality of protrusions.
 15. A high-functional freezing apparatusaccording to claim 1, further comprises air blowing means for blowingcold air in the freezer to the object and an ionic air generator foradding ionic air to the cold air blown from the air blowing means.
 16. Ahigh-functional freezing apparatus according to claim 15, wherein theionic air generator comprises a tubular anode, a linear cathode enteringinto the inside of the tubular anode, and a voltage generator forapplying an voltage between the anode and the cathode.
 17. Ahigh-functional freezing apparatus according to claim 16, wherein thetubular anode and the linear cathode are made of stainless steel orsteel plated with silver or gold.
 18. A high-functional freezingapparatus according to claim 1, wherein the surface of the inside wallof the freezer comprises a material capable of absorbing far infraredrays.
 19. A high-functional freezing apparatus according to claim 1,wherein a honeycomb formed of a highly heat-conductive material isprovided in a flow path of the cold air in the freezer.
 20. Ahigh-functional freezing apparatus according to claim 1, wherein thefreezer is part of a refrigerator-freezer so that the frozen object isallowed to be a refrigerated preserve or a fridge-frozen preserve.
 21. Ahigh-functional freezing method, comprising the steps of: placing anobject to be frozen in an internal space of a freezer, quickly coolingthe object to a predetermined temperature with an oscillating electricfield and a alternating magnetic field applied while water is preventedfrom freezing, and subsequent to said cooling step, instantaneouslyfreezing the object at the predetermined temperature with the freshnessmaintained high, wherein, the object is any type of food products, foodstuffs, and organisms, and said cooling and freezing steps achieveshigh-functional freezing by freezing and preserving the object withoutdestructing cells of the object and to suppress nucleation of icecrystals, wherein the oscillating electric field has one of i) avariable frequency which varies continuously in the range of 50 Hz to 5MHz, ii) a variable frequency which varies in stages, step by step, inthe range of 50 Hz to 5 MHz, and iii) an alternative oscillatingfrequency of 250 KHz or 3 MHz.
 22. A high-functional freezing methodaccording to claim 21, wherein the frequency is continuously varied. 23.A high-functional freezing method according to claim 21, wherein themagnetic field is a static magnetic field and/or a variable magneticfield.
 24. A high-functional freezing method according to claim 23,wherein, said cooling step uses a magnetic field-generating means toapply the alternating magnetic field applied while water is preventedfrom freezing, the magnetic field-generating means applying a staticmagnetic field with an intensity of the static magnetic field in therange of 1 to 10,000 Gauss, and applying a variable magnetic field withan intensity of the variable magnetic field in the range of 1 to 1,000Gauss.
 25. A high-functional freezing method according to claim 23,wherein the variable magnetic field is generated by applying analternating current to a plurality of electromagnetic coil unitsdisposed so as to be across a holder or so as to surround or sandwichthe holder holding the object or on which the object is placed in theinternal space of the freezer, and arranged in parallel, in series, orcrosswise along the holder.
 26. A high-functional freezing methodaccording to claim 25, wherein each of the electromagnetic coil unitscomprises: a coil base with a predetermined shape for forming a coil; anelectromagnetic coil formed of a predetermined turns of highlyconductive wire with an insulative coating, wound around the coil base;and a caulking compound sealing the electromagnetic coil.
 27. Ahigh-functional freezing method according to claim 21, wherein ionic airis added to cold air in the freezer.
 28. A high-functional freezingmethod according to claim 21, wherein the surface of inside wall of thefreezer comprise a material capable of absorbing far infrared rays. 29.A high-functional freezing method according to claim 21, wherein thecold air in the freezer is passed through a highly heat-conductivehoneycomb.
 30. A uniform variable magnetic field generator, whichcomprises: a magnetic field generator contained in a thermally insulatedclosed space and a variable magnetic field generator havingelectromagnetic coil units through which an alternating current ispassed to apply a variable magnetic field to an unattached object in theclosed space, the electromagnetic coil units being disposed so as to beable to apply the uniform variable magnetic field to the object, in sucha manner as to be across a holder for placing the object on or holdingthe object, or as to surround or sandwich the holder, and a plurality ofelectromagnetic coil units is arranged in parallel, in series, orcrosswise along the holder, wherein each of the electromagnetic coilunits comprises: a coil base with a predetermined shape for forming acoil; an electromagnetic coil formed of a predetermined turns of highlyconductive wire with an insulative coating, wound around the base; and acaulking compound sealing the electromagnetic coil.
 31. A uniformvariable magnetic field generator according to claim 30, wherein thecoil base comprises an electrically insulative, water-resistant,heat-resistant, and magnetically permeable material.
 32. A uniformvariable magnetic field generator according to claim 31, wherein thematerial is a plastic.
 33. A uniform variable magnetic field generatoraccording to claim 30, wherein the electromagnetic coil units aremovably disposed.
 34. A freezing apparatus including the uniformvariable magnetic field generator as set forth in claim
 30. 35. Ahigh-functional freezing apparatus according to claim 1, wherein, theoscillating electric field-generating means comprises i) a pair ofelectrodes (3 a, 3 b) opposing each other to sandwich the object (2),and ii) an oscillating electric field generator (3 c) applying anoscillating electric field between the pair of electrodes (3 a, 3 b) toapply the oscillating electric field (31) to the object (2) through thepair of electrodes (3 a, 3 b), the oscillating electric field generator(3 c) comprising a frequency generator to vary the frequency, and anamplifier circuit to apply an electric field with an intensity in therange of 100 to 5,000 V/cm to the pair of electrodes, the oscillatingelectric field-generating means configured to i) provide the oscillatingelectric field to cool the object to a predetermined temperature whilewater is prevented from freezing, and ii) eliminate growing ice crystalnucleuses while achieving a supercooling state at the predeterminedtemperature, the predetermined temperature is the range of −20 to −40°C., and the magnetic field-generating means for applying a magneticfield to the object comprises i) a static magnetic field-generatingmeans (6 a) for generating a static magnetic field, and ii) a variablemagnetic field-generating means (6 b) for generating a variable magneticfield, the static magnetic field-generating means disposed withpolarities aligned so that the static magnetic field acts on the objectwith a static magnetic field having an intensity in the range of 1 to10,000 Gauss, and the variable magnetic field-generating means (6 b)provides a variable magnetic field whose direction is variedperiodically by passing an alternating current with a constant frequencythrough a coil to develop an intensity of the variable magnetic field inthe range of 1 to 1,000 Gauss, the variable magnetic field arranged toact on the object uniformly and effectively prevent the nucleation ofice crystals.